The invention relates to ties which can be used in coextrusion, comprising biorenewable and/or biodegradable polymers that have good adhesion properties, these ties being used in multilayer structures. The various layers are preferably made with biorenewable and/or biodegradable compounds or compositions. These multilayer structures are advantageously used in the field of food packaging.
The term “biorenewable or renewable” applies to a natural resource, the stock of which may be regenerated over a short period on the human scale. In this case, the renewable-based materials correspond to organic materials whose carbons come from non-fossil resources (see ASTM D 6866).
The term “biodegradable” applies to a material that is degraded by microorganisms. The result of this degradation is the formation of water, CO2 and/or CH4 and, optionally, by-products (residues, new biomass) that are not toxic for the environment.
The (renewable—or biodegradable-based) “biopolymer” market is expanding rapidly, especially in food packaging. This expansion is due to the need to find an alternative to fossil materials and to reduce pollution. The potentiality of biorenewable and/or biodegradable polymers, for example polylactides or polyhydroxy alkanoates, no longer has to be proved. These polymers have a limited impact on the environment in comparison with polymers resulting from non-biodegradable fossil resources. Biorenewable polymers make it possible to limit the consumption of fossil materials and to make use of resources originating from the growing of plants. Biodegradable polymers are themselves rapidly converted to products which may, partly or completely, be absorbed by the plants present in the environment.
However, these biopolymers taken separately cannot fulfil all the specifications generally demanded in the packaging industry. Specifically, in this sector, the structures used must have, in particular, mechanical properties, barrier properties to water and to gas and/or sufficient weldability.